Ho pioneered theoretical studies of BEC. He has made a wide range of contributions in the field, for which he was awarded the 2008 Lars Onsager Prize of the American Physical Society. Recently, he has worked on the physics of cold atoms in optical lattices, and has pointed out the amount of cooling needed to meet the DARPA challenge.
The new method cools the atoms in an optical lattice by literally squeezing the heat out of them and into a surrounding BEC, which acts as a heat sink.
Ho has already shared the cooling method with the three teams in recent DARPA Meetings. The teams are led by the Massachusetts Institute of Technology, Rice University, and the University of Maryland. Each team is approaching the problem a little differently, and Ho is a member of two of the teams: Rice and Maryland.
All are working to create an optical lattice -- a three-dimensional cubic structure made of laser light which contains many smaller cubes, or "cells," inside it. Each cell in the lattice is supposed to contain one atom.
If the researchers succeed, they will have made an adjustable crystal out of laser light, and will be able to emulate different solid materials.
Physicists think of heat in terms of entropy, or disorder, Ho explained. His cooling method involves boosting the laser intensity to force the atoms into a very orderly arrangement.
The researchers are trying to trap atomic particles called fermions, which have an internal angular momentum called spin. When fermions are hot, they spin chaotically. The hotter the atoms, the more disordered these spins become.
Ho and Zhou discovered that by raising the laser intensity, researchers could compress the fermions into a so-called "band insulator," where each cell in the lattice contains two fermions instead of one. Each fermion will
|Contact: Tin-Lun Ho|
Ohio State University